Studies of Substituent Effect on Asymmetric Epoxidation of Chromenes by Chiral Dioxirane
摘要:
A series of 6- and 8-substituted chromenes has been investigated for asymmetric epoxidation using chiral ketone catalysts. Up to 93% ee was achieved. Higher ee's are obtained when substrates are substituted at the 6- position. The enhanced enantioselectivity is likely due to the beneficial interaction between the 6-substituent of the substrate and the N-aryl or alkyl group of the ketone catalyst.
ReCl(CO)5-catalyzed cyclocondensation of phenols with 2-methyl-3-butyn-2-ol to afford 2,2-dimethyl-2H-chromenes
作者:Hanxiang Zeng、Jia Ju、Ruimao Hua
DOI:10.1016/j.tetlet.2011.05.093
日期:2011.7
A direct one-pot route for the synthesis of 2,2-dimethyl-2H-chromenes by Re(CO)5Cl-catalyzed cyclocondensation of phenols with 2-methyl-3-butyn-2-ol has been developed. The easy availability of starting materials, mild reaction conditions, high atom-efficiency, and the use of a recoverable catalyst are advantages of this procedure.
2,2-Dimethyl-2H-chromene was prepared from salicylaldehyde and ethyl 3-methyl-2-butenoate (or ethyl α-bromoisobutyrate) in one step. This newmethod of preparing 2,2-dimethyl-2H-chromene was studied and applied to some 2,2-dimethyl-2H-chromene derivatives.
NOVEL DIAZASPIROALKANES AND THEIR USE FOR TREATMENT OF CCR8 MEDIATED DISEASES
申请人:Borjesson Lena
公开号:US20090156575A1
公开(公告)日:2009-06-18
The invention provides compounds of general formula
wherein A, B, p, w, x, y, and z are as defined in the specification, processes for their preparation, pharmaceutical compositions containing them and their use in therapy.
An efficient and simple method for synthesis of 2,2-disubstituted-2H-chromenes by condensation of a phenol with a 1,1-disubstituted propargyl alcohol using BF3·Et2O as the catalyst
An efficient and simple method for the synthesis of 2,2-disubstituted-2H-chromenes by one-step cyclocondensation of a phenol with a variety of 1,1-disubstituted propargyl alcohols using BF3·Et2O as the catalyst is described.